Dead spacecraft helps map Bermuda Triangle of space

Peer into the Bermuda Triangle of space… A European spacecraft has given us a detailed glimpse into a dangerous radiation zone a few hundred kilometres above the coast of Brazil.

The South Atlantic Anomaly (SAA) is the point where the Van Allen radiation belts – rings of charged particles that surround Earth – come closest to the planet’s surface. When the belts were discovered in the 1950s, scientists suspected the SAA could pose some risk.

Sure enough, as spacecraft electronics have become more complex, troubles have been on the rise. Astronauts’ on the space shuttle noticed that their laptop computers would sometimes crash when they passed through the anomaly, and they saw strange lights flash before their eyes. Some spacecraft, such as the Hubble Space Telescope, are programmed to switch off their delicate instruments as they fly through the SAA to avoid damage.

Dangerous diving

Riccardo Campana at the National Institute for Astrophysics in Bologna, Italy, and his colleagues are designing a space telescope that will orbit through the lower part of the danger zone, which is not well studied. “Most radiation models used in planning space missions are based on extrapolations from high-latitude, high-inclination observations,” says Campana, making them less accurate for different types of orbits.

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To better assess the risk, they analysed radiation data from an X-ray-monitoring satellite called BeppoSAX, which was active from 1996 to 2003. It had a similar orbit to the one planned for the new telescope, which meant it regularly dove through the edge of the SAA – and it had been equipped with a radiation detector.

They found that radiation levels in the lower layer of the SAA were much less than in the upper layers. They also saw that the anomaly is slowly moving westwards. This is broadly in line with data from another satellite that was analysed in 2009, which covered the central region of the SAA. The BeppoSAX data can now be added to existing maps of the region, giving a fuller picture.